Stud welding device



Jan. 29, 1957 T. E. SHOUP ET A1. 2,779,859

STUD WELDING DEVICE 39 4i *L -licks (do @j Heks [40 im;

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Jan. 29, 1957 T. E. SHOUP ET AL STUD WELDING DEVICE 2 Sheets-Sheet 2Filed NOV, l2, 1954 mm mw /v/es m HCR.;

INVENTOR.

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STUD WELDENG DEVICE Application November 12, 1954, Serial No. 468,376

14 Claims. (Cl. 219-98) This invention relates to a new method,apparatus and circuits for controlling stud welding and drip or spotwelding wherein the stud is not plunged into the molten metal.

In the majority of stud welding equipment on the market the stud isconnected to one side of a source of welding current and a plate towhich the stud is to be welded is connected to the other side of thesource of welding current. in the most popular equipment a solenoid in astud welding gun is connected in series with the stud. As soon aswelding current starts to flow through the solenoid, the stud and plate,the solenoid retracts the stud from the plate to draw an are between thestud and the plate. This arc is initiated by the welding current whichflows through the solenoid. After the arc has continued for a definiteperiod of time sucient to melt the end of the stud and the plate, thesource of welding current is disconnected and the stud is plunged intothe plate. This apparatus and method has produced excellent results onstuds of various diameters and materials.

in another type of stud welding wherein an arc is drawn between the studand the plate, the stud was also lifted from the plate to establish anarc oy a solenoid. However, the solenoid was powered by a circuitentirely independent of the welding circuit. A design of this typerequired very close control of the switches and contactors in bothcircuits to ensure correct timing of operation.

in another type of stud welding a high frequency current superimposed onthe welding current has been used to initiate an arc between the studand the plate. This type of equipment does not necessarily need asolenoid since the stud can be positioned at the arc distance from theplate and the high frequency current will span the gap to initiate anarc.

in another of the prior devices a solenoid was used to lift the studfrom the plate to establish an are. In this -device a solenoid, thestud, and the plate were connected in series to a source of relativelylow current value. The sole purpose of this low current was to lift thestud and strike an are. The welding current source was then connected tothe stud and plate with the welding current also ilowing through the arcto melt the end of the stud and the plate. In this device separatesources of current were needed for the welding and for the arcinitiating current. The arc initiating current flowed throughout theentire duration of the ow of welding current.

These prior devices which require two sources of cur rent, do not lendthemselves to a portable hand tool which can easily be moved from placeto place. Many applications of stud welding are performed from batterypower, rectiers or motor generator sets, in such places as newconstruction, steel mills, etc. Many times on construction jobs and evenin other locations portable power units must be used for the welding. Ifthe stud welding equipment will Work on a single source of power, thecost and amount of equipment needed 'for power is arent 2,779,859Patented Jan. 29, 19,57

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M greatly reduced. It is only necessary to supply one power source forthe present invention.

in drip welding the stud is lifted from the plate to draw an arc and aportion of the end of the stud is melted. This melted portion of thestud drips into the work plate to form tile weld. However, the stud isheld away from the work plate until after the molten metal hardens sothat the inain oody of the stud will not become welded to the plate.When a non-consumable stud is used only the por; tion of the plate ismelted by the arc. Best results are obtained when the noirconsumablestud is maintained away from the plate until after the molten materialin the plate has hardened to form the weld.

@ne of the objects of the invention is to provide a portable studwelding tool which will operate from a single source of power and whichis adapted to weld many sizes of studs.

Another object of the invention is to provide a stud welding device andmethod which lends itself to a small, compact, lightweight hand toolwhich will accommodate studs of many sizes.

Another object of the invention is to provide a stud welding device inwhich the lifting current is not Varied by variations in the weldingcurrent even though both currents are obtained from the same source ofpower.

Another object of the invention is to provide a stud welding hand toolwhich will weld studs from approximately 1/s diameter to over 11/2diameter without excessive heating of the hand tool.

Another object of the invention is to provide a method of stud weldingwherein the stud, plate and a lifting coil are connected in series to asource of current followed by the connecting of the source of currentdirectly to the stud and plate to melt the end of the stud andsimultaneously shunt the lifting coil to render it ineffective and nallyplunging the stud into the plate and disconnecting the source ofcurrent.

Another object of the invention is to provide a method of stud weldingwherein the lifting coil is shunted by the connecting of the source ofcurrent to the stud and wherein a holding coil simultaneously energizedto hold the stud at the arc distance from the plate.

Another object of the invention is to provide a welding circuit whereina stud is lifted from a plate to draw a welding arc, the welding arc ismaintained for a definite period of time and the stud is held away fromthe plate for a longer period of time to allow molten metal in the plateto harden after the arc is extinguished.

Another object of the invention is to provide a stud welder with a firstcircuit including a lifting coil to lift the stud from the plate andstrike an arc therebetween, a second circuit including a holding coil tomaintain the stud in lifted position and maintain a welding arc betweenthe stud and plate, and a control circuit controlling these first andsecond circuits with the control circuit having inherent capabilities tomaintain the first circuit after de-energizing the second circuit tokeep the stud lifted after the welding arc is extinguished so that thestud will not be plunged into the molten metal of the plate.

Other objects and a fuller understanding of the invention will becomeapparent from the description and claims and the drawings in which:

Figure l is a schematic illustration of the preferred stud weldingcircui-t;

Figures 2 and 3 are modifications of the circuit of Figure l for dripwelding; and

Figures 4, 5, 6 and 7 are other modifications of stud welding circuitswhich are adaptable to drip or spot welding.

The gun and solenoid used in the present invention `are the same as thatused in our pending application Serial d? Number 421,780, tiled April 8,1954, entitled Stud Welding Method and Device. For this reason only thenecessary parts of the gun and solenoid are schematically illustratedand demonstrated here to point out the mode of operation of the weldingcurrents and the methods of vwelding applied by using the circuits. Asin the pending patent application, the gun has a solenoid coil 13, astud holder 21 and a stud plunger spring 22. The solenoid coil 13 iscapable of overcoming the stud plunger spring 22 for lifting a stud Sfrom a work plate W to hold it in a predetermined position at a definitedistance from the work plate for a definite period of time. When thesolenoid coil 13 is de-energized, the plunger spring 22 plunges the studin the work plate W.

The stud welding circuit illustrated in Figure l includes a weldingcontactor C1 and its contactor coil C which is controlled by a normallyclosed time delay relay switch TR and its delay coil TD and controlrelay switches CR1, CRZ, CR3 and CR4 and their control relay coil CR.One end of the solenoid coil 13 is connected by yau end lead 14 to oneside 31 of a source of welding power P. The other end of the coil 13 isconnected by an end lead 15 to one side of the control relay switch CR4and a lead 36 connects the other side of the control relay switch CR4 tothe other side 32 of the welding Vcurrent source of power P. One side ofthe welding contactor C1 is connected directly to the side 31 of thewelding current source and the other side of the contactor C1 isconnected by suitable welding cable 2d to the stud holder 21. Thecontrol relay switch CR1 has one side thereof connected to the weldingcable 21) and the other side thereof connected by a lead 16 to thesolenoid coil 13 `at a point between the ends thereof. That portion ofthe solenoid coil 13 which is between the lead 14 and lthe lead 16 istermed the liftmg portion and that portion of the coil between the lead1S and the lead 16 is termed the holding portion of the coil.

Also connected to the side 31 of the welding current source by a lead 18is the gun button F which is also connes-ted by a lead 19 to one side ofthe time delay relay switch TR and one side of the time delay coil TD. Alead 34 connects the other side of the time delay relay switch TR to oneside of the control relay coil CR and a lead 3S connects the other sideof the control relay coil CR to the side of the power source P.Similarly a lead 36 connects the other side of the time relay coil TD toKthe power side 32. The control relay switch CRZ has one side thereofconnected by lead 37 to power source side 31 and the other side thereofconnected by lead 38 to the previously mentioned lead 19. The controlrelay switch CR3 has one side thereof connected by lead 39 to side 31 ofpower source P and the other side Ithereof connected by lead 4% to oneside of the contactor coil C, the other side Iof which is connected toside 32 of the welding current source P by lead 41.

The welding and control circuit of Figure l operates as follows: After astud is placed in the gun and positioned against the work plate W, theoperator closes the gun button F to electrically connect leads 18 and19. This starts a relatively low current owing through leads 18 and 19,time delay coil TD and lead 36 to energize the time delay coil TD.Current also flows through leads 18, 19, 34 and 35 and normally closedtime delay relay switch TR to energize control relay coil CR.Energization of ,control relay coil CR causes it to close control relayswitches CR1, CRZ, CRS and CR4. The closing of switch CR2 shunts orinterlocks the gun button F with current flowing through leads v37 and38 to lead 19 to maintainenergization of control relay coil CR and timedelay coil TD in case the gun button F Yis released or opened duringwelding. The closing of control relay switch CR1 allows current to ilowfrom the welding current source P through leads 31 and 1li, the solenoidcoil 13, through lead 16, control relay switch CR1, welding cable 2t),stud holder 21, stud S, work plate W and lead 32 to the opposite side ofthe welding current source P. This lifting portion of coil 13 limits thecurrent to a relatively small current ilow which is sufficient to causethe lcoil 13 to lift the stud S from the plate W and strike a pilot arcbetween the stud and plate.

The control relay switch CRS is closed simultaneously with switch CR1and current flow is established from the power source on the side 31 toside 32 through leads 39, 40 and 41 and the contacter coil C and at thesame time the solenoid coil is energized to strike the arc. As soon ascontactor coil C is energized, it closes contaotor C1 allowing weldingcurrent to flow from power source side 31 through welding cable 2%, studholder 21, stud S, the arc and plate W to side 32. The closing oflcontactor C1 shunts control relay switch CR1 and the lifting portion ofthe coil 13 thereby rendering the lifting portion of the coil 13ineffective and ycompletely substituting a full welding arc for thepilot arc. Simultaneously the holding portion of the coil 13 becomeseiective due tothe resistance of 4the welding arc to hold the stud Slifted from the plate W to maintain the welding arc. After a defini-teperiod of time, -time delay `relay switch TR opens, de-energizingcontrol relay coil CR to open control relay switches CR1, CE2, CR3 andCR4. Opening the control relay switch CRS de-energizes contacter coil Cto open contactor C1 and stop the ow of welding current. After ytimedelay coil TD is de-energized by opening control relay switch CR2, timedelay relay -switch TR `returns to its normally closed position. All ofthe switches are now in their original position whereby a new stud maybe inserted in the stud holder. By opening the switches CR1 and CR4current is completely removed from the solenoid coil `to permit plungingof the stud at the correct instant relative to opening the weldingcontactor C1. Opening these switches also cancels any residual eectswhich might be built up to continue tlow of current 'through the holdingportion of ythe coil 13, switches CR1 and CR4, the stud and plate W.

The circuit illustrated in Figure 2 is generally similar to that ofFigure 1. However, in Figure 2 a noplunge switch NP, no-plunge relaycoil NPR, and a no-plunge relay switch NPR1 have been added to thecircuit. The 11o-plunge switch NP and the rio-plunge relay coil NPR areconnected in series in leads i2 between lead 19 and the side 32 of thesource of power P. The no-plunge relay switch NPR1 is similarlyconnected by lead 43 between the lead 15 from the one end of thesolenoid coil and the power source side 32 so that the switch NPR1 is inparallel circuit with the contactor relay switch CPA. The no-plungeswitch NP is a manually `operated switch which when in open positionpermits the circuits to operate the same as in Figure l. However, whenthe noplunge switch NP is closed, the operator can continue the flow ofcurrent through the no-plunge coil NPR to hold the stud away from theplate after the contactor C1 and the control relay switches CR1 and CRAopen by holding the button F closed. As long as the button F is heldclosed, the no-plunge coil NPR is energized to keep the 11o-plungeswitch NPR closed and energize solenoid coil 13 through leads 14 and113.

The modied circuit in Figure 3, like that 'of Figure 2, may be used toprevent plunging of the stud after the welding current has been shut offso that the main body of the stud cannot become welded to the workplate.

. This modification includes the same circuit as used in Figure 1 andadds to it a timing circuit which will prevent plunging of the studuntil after the molten metal has hardened. The timing circuit forperforming this function includes no-plunge switch N, no-plunge coil NRand its no-plunge relay switches NR. and NR2, no-plunge time delay coilTDN and a no-plunge time delay switch TDR. 1n this circuit one side ofthe rio-plunge switch N is connected to the lead 19 and the other sideis connected by a lead 45 to one side of the no-plunge time delay coilTDN, the other side of which is connected armeno to side 32 ot' thepower supply by a lead 46. One side of the no-plunge time delay switchTDR is connected by a lead 47 to the lead 45 and the other side of thisswitch TDR is connected by lead 48 to the no-plunge coil NR, the otherside of which is connected directly to the side 32 of the power supplyby a lead 49. The rio-plunge relay switch NRT has one side thereofconnected to the Side 3l of the power supply and the other side thereofconnected to the lead 38 so that it operates in parallel with 'thecontrol relay switch CRZ. imilarly one side ot the rio-plunge relayswitch NR2 is cc-Jurccted to thc `lead i5 and the other side isconnected to the side 32 of the power supply so that it operates inparallel with the control relay switch CR4.

When rio-plunge switch N is open, the circuit of Figure 3 operates thesame as the circuit of Figure l. However, when the switch N is closed,the no-plunge circuit functions to prevent plunging of the stud afterthe welding current is shut oli by opening contactor Cl.

T his circuit operates in the following manner when the no-p1unge switchN is closed. Closing finger button switch F energizes rio-plunge timedelay coil TDN at the same time ti e time delay coil TD is energized,simultaneously passing current through the normally closed 1ro-plungetime delay switch TDR and the rio-plunge coil NR. Energizing of theno-plunge coil NR closes noplunge relay switches NRT and NRZ the same asthe control relay coil CR closes the switches CRE and CR. The rio-plungetime delay switch TDR is manually adjusted that it stays closed a longerperiod ot time than the time delay relay switch TR, thus permitting theopening of the switches CRT, CRZ, CRS and CRt prior to the opening otthe switches NRT and NR-.2. The weldwir .g contactor thus is also openedprio-r to the opening of the no-plunge relay switches (NRT and NRZ.

After the switches CRT and CRiI have been opened and the welding currentcontactor Cl has been opened, a small amount ot current flows throughthe lead ltd, coil i3, lead l5, switch NRZ to keep the coil energizedand maintain the stud lifted from the plate. When the nti-plunge timedelay switch TDR opens the 11o-plunge coil NR is deenergized, thusre-opening the switches NRT and NRE. This breaks the solenoid circuitand allows the stud to plunge and returns the circuit to originalposition for another operation. The molten metal at the end or" the studon the adjacent work plate W has hardened by this time so that the stu-ddoes not become welded to the work plate when it is plunged therein.

A very simple circuit, which will control the time of ow `of the weldingcurrent and yet permit the holding oi' the stud away `from the plateuntil after the weld metal hardens, is illustrated in Figure Lt. in thiscircuit the solenoid coil 13 has one end thereof connected through ahold switch Hl to the side 3l ot' the source of power P by lead Sl. Theother side of the solenoid coil 13 is connected by lead 52 to the otherside 32 of the power source. As in the other figures one side of thewelding contactor Cll is connected directly to the one side et thewelding power source and the other side of the welding contactor isconnected by welding cable Ztl to the stud holder 2l. In this circuitthe center tup ot the solenoid 113 is connected by lead :S3 directly tothe welding cable 2%.

The timing control includes the regular gun button or `linger switch F,the time delay relay switch TR, the time delay coil TD and the controlrelay coil CR, which are connected in the same manner and as illustratedin Figure l. Therefore, the reference characters i8, lil, 3d, and 3o ofFigure l refer to the same lead wires in Fi One side of the hold coil His connected to the lead i? and the other side of the hold coil H isconnected to the side of the power source F. Also as in thecircuitvdiagram of Figure l, the control relay switch CRS and thecontactor coil C are connected between the sides 31 and 32 of the powersource by the leads 39, 40 and 41.

This circuit of Figure 4 operates as follows: Closing finger switch Fcauses current to ilow through time delay relay switch TR, control relayCR, time delay coil TD and hold coil H. Hold coil H closes hold switchHi to initiate current ow through a portion of the solenoid coil 13 andthe stud so that the stud is lifted from the plate and an arc is struck.Energizing control relay coil CR closes control relay switch CRS whichin turn cnet contactor coil C to close the welding contactor Cl therebyincreasing the current tlowing through the arc to full welding current.After a predetermined interval of time the time delay relay switch TRopens deenergizing control relay coil CR thus opening control relayswitch CRS to de-energize contactor coil C and open the welding currentcontactor C1 thus stopping the ilow `ot welding current through the arc.Continued holding of the nger switch F closed allows current to tiowthrough the hold coil H, thereby holding the hold switch Hl closed tokeep the solenoid i3 energized and keep the stud lifted from the plateafter welding current has been stopped. This continued holding currentilows through the solenoid and leads 5l and S2 and not through the gapbetween the stud and the work plate. The stud will be held lifted aslong as the linger switch F remains closed.

The circuit oi Figure 5 is similar to that of Figure 4. However, in thecircuit of Figure 5 a switch CRS replaces tie switch Hl, switch CRS isoperated and controlled directly by the coil CR. A resistance R has alsobeen added between the leads i9 and 2d so that a light current can flowthrough switch CR2, resistance R, part ot solenoid i3 and lead 52 tohold the stud lifted from the plate after contactor Cl and switch CREShave been opened. ln this circuit the welding operation is initiated byclosing the linger switch F. However, if the ringer switch F is held inthe closed position until after the completion of the welding currentcycle, the current will continue to tlow through the switch F,resistance R, and part of the solenoid, to maintain the stud lifted fromthe plate after welding current flow has stopped, the same as is done inFigure 4 by holding the switch F closed.

ln Figure 6 one side of the solenoid coil 13 is connected throughilo-plunge time delay switch NR7 to side 3l of the power source P andthe other end of the solenoicl coil 13 is connected by lead 5d to theside 32 of the power source P. As in the previous circuits, weldingcontactor Cl is connected to side 31 of the power source P and to thestud holder Zi by welding cable 2d. The center of the solenoid coil 13is also connected to the welding cable 2t). In this circuit theinitiating of the arc and the energization of the solenoid coil i3 bymeans of no-plunge time delay switch NR7 is controlled by a circuit,including gun button switch F, rio-plunge time delay switch TDR,no-plunge coil NR, no-plunge time delay switch NRS, and no-plunge timedelay coil TDN. The flow of welding current is controlled by weldingcontactor Cl operated by contactor coil C which is energized throughcontrol relay switch CRS. This control relay switch CRS is controlled bycontrol relay coil CR which is in a circuit including switch NR9, timedelay relay switch TR and time delay coil TD. One side of each of theswitches F, NRS, NR9 and CRS is connected to the side 31 of the powersource. The other side of the switch F is connected by lead 6d to oneside of the no-plunge time delay switch TDR and one side of theno-plunge time delay coil TDN. The other side of the no-plunge timedelay switch TDR is connected by lead to one side o the no-plunge coilNR, the other side of which is connected by lead 66 to the side 32 ofthe power source. The lead d4 also connects the opposite side of thenoplunge time delay switch NRS to one side of the noentrasse plunge timedelay coil TDN the opposite side of which is connected by lead 67 toside 32 of the power source P. Similarly lead 65 connects the oppositeside of the switch NR9 to one side of the time delay relay switch TRwhich is connected by lead 69 to the control relay coil CR, the otherside of which is connected directly to the side 32 of the power source.Lead 68 is also connected to one side of the time delay coil TD, theother side of which is connected directly to the power source side 32.The control relay switch CR3 is connected by lead 70 to one side of thecontacter coil C, the other side of which is connected to the side 32 ofthe power source P.

The circuit of Figure 6 operates as follows. When finger button switch Fis closed, current llows through the lead 64, normally closed switch TDRand coils NR and TDN to energize these coils NR and TDN. Coil NR closesswitches NR7, NR and NR9. Closing switch NR9 energizes coil CR throughnormally closed switch TR and also energizes coil TD. When coil CR isenergized, it closes the switch CRS energizing coil C and closing thewelding contacter Cl. Prior to this, however, the welding arc has beeninitiated and the stud lifted from the plate by the solenoid i3, sincethe switch NR7 was closed before the welding contacter Cl was closed.When the welding contacter C1 is closed, it shunts out the switch NR?and expands the pilot arc to full welding current arc. After apredetermined time the switch TR opens, thus de-energizing coil CR toopen the contactor Ci and stop the welding current. When the weldingcontactor Cl is opened, current again begins to flow through the switchNR'I', and the coil 13 thus holding the stud at the arc distance awayfrom the work plate and preventing plunging of the stud. After a furtherpredetermined time the switch TDR opens, thus deenergizing coil NR andopening the switches NR', NRS and NR9. Opening of the switch NR7de-energizes the solenoid coil i3 and opening of the other switchesreturns the circuit to its initial position. It is noted with thiscircuit that the linger switch F does not have to be held closedthroughout the duration of the cycle since it is shunted and interlockedby the switch NRS.

The circuit of Figure 7 performs substantially the same function as thatof Figure 6. In many respects the circuits are similar. However, inFigure 7 the no-plunge time delay switch NR7 has been replaced by acontrol relay switch CR which is operated and controlled by the coilcontrol relay CR, instead of being operated and controlled by theno-plunge coil NR. In this circuit a resistance R has also been insertedbetween leads 26 and 64. In this circuit the switch CRS is opened justprior to the opening of the welding current contactor C1. The solenoidcoil continues to maintain the stud in its lifted position after theopening of the switches CRS and Cl by means of the resistance R. Currentows through the switch NRt, resistance R. hold portion of coil id andlead 54 so long as the switch NRS is held in closed position by the coilNR. However, after the switch TDR has timed out, it opens to de-energizethe coil NR and open switch NRS so that all current ow is removed fromthe solenoid coil i3 and the stud is allowed to plunge against theplate. Switch TDR times out later than switch TR so that the studsplunge after the molten metai has hardened, thereby preventing weldingof the stud to the plate W.

In the various circuits we have described using a relatively low currentthrough the lifting portion of the coil and through the holding portionof the coil as compared to the welding current. in actual practice wehave been able to weld studs with the current going through the liftingportion of the coil to strike the pilot arc being in the neighborhood of10 to l0 amperes. A, full welding current may lie-anywhere from 30G to5000 amperes or larger depending on the stud being welded. In this sameAinstance the current flowing through the holding portion of the coilduring the actual welding was only in the neighborhood of l ampere. Itis understood that these specic values were used in a particular set-upand that the values may be changed if the need arises.

Although this invention has been described in its preferred form with acertain degree of particularity enabling others to reproduce theinvention, it is understood that the present disclosure has been made byway of example and that numerous modifications and changes in thedetails may be resorted to without departing from the spirit and scopeof the invention as deiined in the claims which are made a part hereof.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. An electrical circuit for a stud Welder adapted to lift a stud from aWork piece to draw an arc therebetween, said circuit comprising, a rstcircuit including a lifting coil to lift the stud from the plate andstrike an arc therebetween, a second circuit to maintain a welding arcbetween the stud and plate and including a holding coil to maintain thestud in lifted position, and a control circuit operatively connectedwith said tirst and second circuits to maintain energization of at leastone of said coils to keep the stud lifted while effectingde-energization of the welding arc, said control circuit having timermeans therein.

2. The electrical circuit of claim l wherein said timer means in saidcontrol circuit includes a irst timer controlling the second circuit anda second timer controlling the tirst circuit and the energization of theiirst timer.

3. The structure of claim l including an electrical connection betweenthe rst and second circuit with a portion of the second circuiteffectively shunting at least the lifting coil in the iirst circuitwhile the second circuit is energized.

4. The structure of claim l including switches in said iirst and secondcircuits and an electrical connection between the iirst and secondcircuits with the switch in the second circuit effectively shunting theswitch and lifting coil in the first circuit while the switch in thesecond circuit is closed.

5. The electrical circuit of claim 4 wherein said timer means in saidcontrol circuit includes a rst timer controlling the switch in thesecond circuit and a second timer controlling the rst circuit and theswitch in the energization of the iirst timer.

6. In a stud welding device having a supporting structure, the provisionof a stud carrying member, resilient means urging the stud carryingmember away from the supporting structure, a solenoid in the supportingstructure including an armature operatively connected to the studcarrying member and a coil capable of overcoming the resilient means anddrawing the armature and the stud carrying member towards the supportingstructure, iirst means including a rst switch for connecting one end ofthe solenoid coil to one side of a welding current source, a lead forconnecting the other end of the solenoid coil to the other side of awelding current source, a second means including a contacter forconnecting the stud carrying member to the said one side of the weldingcurrent source, third means for electrically connecting the studcarrying member to the solenoid coil at a point between the endsthereof, a weld timing circuit connected electrically in parallel withsaid rst means, said coil and said lead, said timing circuit including amanually operable switch to energize the timing circuit and timing meansto control said rst switch and said contactor, and a resistance elementelectrically connected between said manually operable switch and saidthird means.

7. The structure of claim 6 including a relay consisting of normallyopen points in parallel with the switch in the first means and a pointclosing coil in series with the manually operable switch.

8. ln a stud welding device having a supporting structure, the provisionof a housing, a stud carrying member in said housing, resilient meansurging the stud carrying member away from the housing, a solenoid in thehousing operatively connected to the stud carrying member and capable ofovercoming the resilient means and drawing the carrying member towardsthe housing, a r'irst circuit including a switch connecting at least aiirst part of said solenoid in series with said stud carrying member, asecond circuit including a contacter at least a second part of saidsolenoid, timing means controlling said switch and said contacter, and athird circuit including a manually operable switch and a resistanceelement connected in series, said third circuit being electricallyconnected in parallel with said contacter to continue flow of currentthrough said second part of said solenoid after the contactor hasopened.

9. The structure of claim 8 including a relay consisting of normallyopen points in parallel with the switch in the rst circuit and a pointclosing coil in series with the manually operable switch.

l0. An electrical circuit for a stud Welder adapted to lift stud from awork piece to draw an arc therebetween, said circ"it comprising, a'first lcircuit including a lifting coil to litt the stud from the plateand strike an arc therebetween, a second circuit including a holdingcoil to maintain the stud in lifted position and maintain a welding arcbetween the stud and plate, and a control circuit controlling said tirstand second circuits.

11. i'n a stud welding device having a supporting structure, theprovision of a stud carrying member', resilient means urging ythe studcarrying member away from the supporting structure, a solenoid in thesupporting structure including an armature operatively connected to thestud carrying member and a coil capable of overcoming the resilientmeans and drawing the armature and the stud carrying member towards thesupporting structure, tirst means for connecting one end of the solenoidcoil to one side of a welding current source, second means forconnecting the other end of the solenoid coil to the other side of awelding current source, third means including a contacter connecting thestud carrying member to the said first means, fourth means electricallyconnecting the stud carrying member to the solenoid coil at a pointbetween the ends thereof, said second and fourth means each switch, aweld timing circuit connected electricnlly in parallel with said tirstmeans, said coil and said second means, said timing circuit including amanually operable switch to energize the timing circuit and timing meansto control said switches in said second and fourth means and saidcontacter.

l2. ln a stud welding device having a supporting structure, theprovision of a stud carrying member, resilient means urging the studcarrying member away from the supporting structure, a solenoid in thesupporting structure including an armature operatively connected to thestud carrying member and a coil capable of overcoming the resilientmeans and drawing the armature and the stud carrying member towards thesupporting structure, rst means for connecting one end of the solenoidcoil to one side of a welding current source, second means forconnecting the other end of the solenoid coil to the other side of aWelding current source, third means including a contactor connecting thestud carrying member to the said first means, fourth means electricallyconnecting the stud carrying member to the solenoid coil at a pointbetween the ends thereof, at least one of said means having a rstswitch, a weld timing circuit connected electrically in parallel withsaid irst means, said coil and said second means to control said lirstswitch and said contacter.

13. An electrical circuit for a stud Welder adapted to lift a stud froma work piece to draw an arc therebetween, said circuit comprising, afirst circuit including a lifting coil to lift the stud from the plateand strike an arc therebetween, a iirst switch in said first circuit inseries with said lifting coil, a second circuit including a contactor, aholding coil and a second switch to maintain the stud in lifted positionand maintain a welding arc between the stud and plate, one end of saidlifting coil and one end of said holding coil being permanentlyelectrically joined together', and a control circuit controlling saidrst and second switches and said contacter.

14. An electrical circuit for a stud Welder adapted to lift a stud froma work piece to draw an arc therebetween, said circuit comprising, afirst circuit including a lifting coil to lift the stud from the plateand strike an arc therebetween, a first switch in said first circuit inseries with said lifting coil, a second circuit including a contacter,said rst switch, a holding coil and a second switch to maintain the studin lifted position and maintain a Welding arc between the stud andplate, and a control circuit controlling said first and second switchesand said contacter.

References Cited in the file of this patent UNITED STATES PATENTS2,265,169 Hughes et al. e Dec. 9, 1941 2,342,144 Hughes Feb. 22, 19442,356,320 Hughes Aug. 22, 1944

